Diameter of air lines

My stationary air compressor has a 1/2" NPT fitting for the output.

I will be using copper pipe for my air piping. Should I use 1/2" or 3/4" copper pipe for my main lines? The internal diameter of 1/2" copper pipe seems awful small. (Yes, industry does use copper for air piping.)

Brian Elfert

Reply to
Brian Elfert
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Depends on what you want as a final result. The 1/2" line will carry more air than the tool can use of the compressor can put out. I don't have my reference book here, but that size will pass an incredible amount of cfm.

The 3/4" line will hold more volume, increasing the total storage capacity for the system. You could go to a 3" or 6" line, but that is not very cost effective for a small shop. We use 4" at work but our air use is much different than a single tool. The large pipe holds a reservoir of air for when the "injectors" we use to fill molds go off. Maybe 36 of them for a blast of 10 seconds or so. An air wrench will never take that much from the system. Look at the size of the hole in the fitting. You never need more than that. Ed snipped-for-privacy@snet.net

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Reply to
Edwin Pawlowski

A larger diameter will provide more volume transfer and faster recovery. That may or may not be important, depending on what tools you plan to use. If you are not sure, use the 3/4".

Reply to
Phisherman

If I needed to supply 8 CFM at 100 PSI, would 1/2" copper be good enough?

Seperate issue:

Could I run compressed air 100 feet underground to a shed and still get 8 CFM at 100 PSI? I'm trying to figure out if I need to buy a seperate compressor.

Brian Elfert

Reply to
Brian Elfert

A 1/16" dia line will supply 6.5 cfm @ 100 psi A 3/32" dia line will supply 14.6 cfm @ 100 psi.

1/4" = 104 cfm

For that distance, I'd go with 3/4". It will supply more air and has greater potential for growth. You'd not want to dig a second trench next year or two. If you got into really large air use, you can install a receiver in the shed. The 3/4" line at that distance should allow at least

30 cfm. Big grinders only use 20 cfm.

For more information, go to Lee Valley and buy the Pocket Reference book. It is about 10 bucks and has all sorts of handy information. Ed snipped-for-privacy@snet.net

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Reply to
Edwin Pawlowski

I used 1/2" copper and it works fine.

Reply to
Larry Bud

Probably not, due to a phenomenon known as head loss. However, you might be able to put an air tank on the end of the line in the shed, and get acceptable intermittent performance.

-- Howard Lee Harkness Texas Certified Concealed Handgun Instructor

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Reply to
Howard

On Mon, 22 Dec 2003 00:14:03 GMT, Howard brought forth from the murky depths:

100' of 1/2" Sch40 steel pipe is good for 15cfm according to the chart on Pg 632 of my Lee Valley copy of Handyman In-Your-Pocket. 0.2500cfs

========================================================== I drank WHAT? +

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Reply to
Larry Jaques

Group: rec.woodworking Date: Sun, Dec 21, 2003, 8:00pm (EST+5) From: snipped-for-privacy@visi.com (Brian=A0Elfert) My stationary air compressor has a 1/2" NPT fitting for the output. I will be using copper pipe for my air piping. Should I use 1/2" or 3/4" copper pipe for my main lines? The internal diameter of 1/2" copper pipe seems awful small. (Yes, industry does use copper for air piping.) Brian Elfert

****************************************************** Please use soft copper tubing and compression fittings no matter what size you choose. Black iron pipe with threaded fittings is also extensively used but requires a pipe cutter and a stock and die. Do not use hard copper tubing and sweated (soldered) fittings. This suggestion is made for obvious safety reasons.

Peace ~ Sir Edgar =F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8= =F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8

Reply to
Sir Edgar

I HOPE there's not a safety issue with using sweated copper for air .. .. .. I just plumbed my whole shop with it !! !! !!

What's the danger ?? ?? ??

Sir Edgar wrote:

I AM NOT PARANOID .. .. .. but EVERYONE thinks I am !! !! !!

Reply to
Anonymous

thus spake:

Not NEAR the danger of using PVC. Copper generally splits open, PVC explodes - sending near supersonic shrapnel everywhere.

Greg G.

Reply to
Greg G.

I have always heard this but I would sure like to see someone demonstrate it. I tried to make a big firecracker with 1/2" PVC and smokless powder when I was young and dumb. It just split open and none of it really turned to shrapnel. That was a lot more than 100PSI. I imagine a decent spud gun is above 100PSI and we don't hear about them > sending near supersonic

Reply to
Greg

Greg thus spake:

All I can relate is the story of a friend who owns a print shop. They have large presses and such that are larger than a bus. He decided to go cheap and install 3/4" PVC pipe for the air feeds - standard 120psi air supply. It exploded several times in various places until he ripped it out and replaced it with copper because a worker was sent to the ER because of flying plastic. I believe it involves long term fatigue cracks in the pipe. OSHA has published several booklets on the how's and why's of NOT using PVC for air supplies.

Greg G.

Reply to
Greg G.

A lot of PVC is not UV stabilized. It can get brittle with age and sunlight exposure. There are also different types of PVC, in both plastic formulation and pipe construction. My PVC DC piping is clearly marked "Not for Pressure" all down the side of each tube.

OSHA forbids PVC pipe under pressure. The 'wreck's FAQ has a link to the actual OSHA article about PVC air pipes.

FWIW, installing iron or copper air pipe is really easy. Since you're using flex hose to the tools and compressor, you only need to get into the vicinity. No precision plumbing is necessary.

Barry

Reply to
B a r r y B u r k e J r .

Bob wrote in reply to my post shown below: Group: rec.woodworking Date: Mon, Dec 22, 2003, 5:17am (EST+5) From: snipped-for-privacy@att.net () I HOPE there's not a safety issue with using sweated copper for air .. . .. I just plumbed my whole shop with it !! !! !! What's the danger ?? ?? ?? Sir Edgar wrote: Brian wrote: Group: rec.woodworking Date: Sun, Dec 21, 2003, 8:00pm (EST+5) From: snipped-for-privacy@visi.com (Brian Elfert) My stationary air compressor has a 1/2" NPT fitting for the output. I will be using copper pipe for my air piping. Should I use 1/2" or 3/4" copper pipe for my main lines? The internal diameter of 1/2" copper pipe seems awful small. (Yes, industry does use copper for air piping.) Brian Elfert

********************************************** Please use soft copper tubing and compression fittings no matter what size you choose. Black iron pipe with threaded fittings is also extensively used but requires a pipe cutter and a stock and die. Do not use hard copper tubing and sweated (soldered) fittings. This suggestion is made for obvious safety reasons. Peace ~ Sir Edgar ****************************************************** Bob ~ Sweated copper piping is used for water piping. If a poorly sweated connection breaks loose there is only inconvenience from the possible water damage that occurs. If a joint fails with a pipe containing compressed air it comes apart with explosive force. You can demonstrate this by removing an air hose under pressure that uses a quick disconnect fitting. Also, most copper tubing is type "M" thin wall type which is made for water service only. There is a type "L" wth a thicker wall. If it were my shop I would redo it using the soft copper tubing and compression fittings. I avoided the expense and trouble of running tubing by installing an industrial type spring return hose reel next to my compressor and 50 ft. of hose. I also have an additional 25 ft. of hose that I can attach to it with a quick disconnect fitting if I need to. I did not mention never to use PVC pipe as I assumed the danger of doing this was well known and I am glad to see that it was covered in other posts. I apologize for the length of this post but I feel that it was warranted from a standpoint of avoiding possible injury to a fellow woodworker.

Peace ~ Sir Edgar =F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8= =F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8=F8

Reply to
Sir Edgar

why? the safety issue isn't clear to me at all. hard copper is probably easier to get a good solder joint with. I cant see rupture or corrosion being an issue with either of them. Bridger

Reply to
nospam

My copper is all in the attic and wall joists .. .. if something ever came apart, I'd certainly hear it but would not see it. When I finished sweating in the whole system, I charged it to over 200psi and left it for about 6 months. It didn't come apart nor did it leak, at least not after I made a few "repairs". I feel sure that this system is as safe as I can make it .. .. .. I don't plan to ever run more than about 125psi on a routine basis. I don't argue the point that it may be possible for a joint to come apart, but I don't see this ever happening in this particular installation., but thanx for the input. I did use the heavier-walled tubing which was recommended by a structural engineer where I work. We have miles of compresses air lines there and it is almost all sweated copper.

I AM NOT PARANOID .. .. .. but EVERYONE thinks I am !! !! !!

Reply to
Anonymous

Hard copper is often used in industrial settings. It is cost effective because it is cheap to install and if you have to make a cut in a line to add another station, copper fittings are generally much easier to work with than iron pipe.

As with any material, care should be used in installation. Any gas under pressure can have disastrous effects if a catastrophic failure should occur. Copper will not "explode" but would split or a fitting could come loose. Ed

Reply to
Edwin Pawlowski

sweated copper done properly is FINE. I checked with the fire department and others when deciding what materials to use for an auto shop air system. Plastic is a definite no-no. There are three kinds of copper pipe, L, K, and M. Get "L"; it's the thickest.

dave

dave

wrote:

Reply to
Bay Area Dave

I know this is the rule and the reasons why PVC might be dangerous, I just don't understand how 120PSI can make 470 lb rated PVC "suddenly explode".

Reply to
Greg

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